Process for producing modified cellulose pulps, cellulose pulp thus obtained and use of biopolymer for producing cellulose pulps

ABSTRACT

The present invention relates to an improved process for producing chemical cellulose pulp wherein biopolymers are added immediately before, during or after a bleaching step, depending on pulp characteristics and on process conditions used. The biopolymers according to the present invention are starch by an etherification reaction. This treatment results in a differentiated pulp having improved physical, chemical and mechanical properties when compared with cellulose pulps obtained by traditional processes. The use of said biopolymer alters the relations between important pulp properties rendering their application in papermaking process advantageous. This differentiation increases the possibilities of use and also of new applications, including for the substitution of pulps produced from other cellulose sources. Thus, the present invention also relates to a process for the preparation of paper, such as printing, writing, decorative, special or tissue-type papers, through the use of the cellulose pulps modified by the above process.

This application is a 371 of PCT/BR11/00071 filed 21 Mar. 2011

FIELD OF THE INVENTION

The present invention relates to a process for the production ofcellulose pulps for enhancing said bleached pulps quality andapplicability, especially their mechanical strength and drainabilityproperties, by incorporating biopolymers specifically developed asadditive into producing process recipe of said differentiated cellulosepulp.

BACKGROUND OF THE INVENTION

In addition to forest developments and treatments directed to papermanufacturing process for developing mechanical strength and otherequally important properties, in the last few years, researchers of thesector have been working on additives association as the most promisingmeans to enhance these properties in cellulose manufacturing processitself. Among the additives that have been used for manufacturing paperare the longer fibers, glues, dry and wet strength agents, starch, andothers.

Document WO 00/28141 describes a method for treating lignocellulosicfibrous materials for enhancing the mechanical strength and humidityproperties of the final product, which comprises fibrous materials, inwhich paper is the major example. The treatment involves the applicationof lignin derivatives in a solvent system with secondary additives whichconsist of a broad scope of sugars and natural polymers. This documentdescribes the addition of additives in the paper machine approach flow,in the so-called wet end of the paper machine, where most additives areincluded in papermaking. Some additives mentioned in that patentapplication are widely known by the properties they provide when used inthe recipe for producing some types (grades) of papers. In addition, theprocess described in that document requires the combination of the useof lignin for obtaining the desired results, which actually correspondsto the innovative aspect of that invention, and other secondary naturalpolymers are included as optional for boosting the development of thedesired properties.

Another document describing the use of (the) biopolymer starch in aprocess for producing cellulose is PI9803764, which relates to a methodfor bleaching cellulose pulp with whitening chemical substances with theaddition of starch, polyvinyl alcohols or enzymes. This documentspecifies the treatment for pulps having more than 5% lignin,emphasizing higher yield pulps such as mechanical pulps,thermomechanical pulps and chemothermomechanical pulps; thus, pulpswithout an ostensive bleaching process such as that of chemical pulps.The object of that invention is only to increase the whiteness of thepulp, and the secondary additives, such as enzymes and starch, are onlyintended to increase the efficacy of the optical whitening agents thusenhancing their absorption on the surface of the treated pulp fibers.These products for enhancing pulp whiteness are added in the last stepbefore drying the pulp and do not develop the mechanical properties ofthe pulp.

Document US49267498 refers to a papermaking process where the additivesare claimed as a retention aid. Therefore, this document teaches apolymer that must be added to the final cellulose pulp very close to thepapermachine to keep a big formed floc and improve drainage. Examples 2and 3 of this document mention a compozil additive, that is, acombination of two products to improve flocculation alone.

Document U.S. Pat. No. 4,756,801 teaches the addition of cationic starchin particular to the papermaking process to obtain a bonding agent inorder to use different kinds of pulps and fillers in the paperproduction. The examples contained in this document again mentionsadditives as retention aids, which is its well known application forpolymers in papermaking processes.

Document EP1080271 exclusively refers to a papermaking process and tothe use of polysaccharides as a retention aid, where a secondary effectcould be the strength. Besides, these polysaccharides must to have anaromatic hydrophobic group. This patent is also related to a minimumconductivity suspension. It is also the case of document EP0148647,which discloses a papermaking process. In the example 1, the applicationof polymer was carried out for softwood (long fibers) and starch wasadded just before the paper sheet formation. The result obtained inaccordance to that example was retention of the pulp suspension duringthe paper sheet formation. Example 2 in turn mentions the combination ofproducts in order to improve retention also using softwood as fiberfurnish. Thus, this document refers to a polymer is used as additive toattach fines and fillers to form flocs and improve retention.

Document WO2004/046464 mentions the treatment of cellulosic materialwith clay and the secondary use of starch or other products as aretention aid. The main objective of this document is to producecellulose with filler, were the secondary additives are only to becomeit possible.

In view of the above, it can be seen that it is already known for priorart to use polymers such as starch but as retention aids in theproduction of paper.

Accordingly, the object of the present invention is the use of abiopolymer during the process for producing cellulose pulp that iscapable to promoting changes in the mechanical properties of the pulp aswell as in other important properties, such as drainage, drying,porosity and pulp refining.

SUMMARY OF THE INVENTION

In a first embodiment, the present invention relates to a process forproducing acid or alkaline cellulose pulps comprising a step of addingat least one biopolymer during the preparation process of said pulps,wherein the biopolymer is a starch modified by an etherificationreaction.

In a second embodiment, the present invention relates to a cellulosepulp obtained by a process of treatment with at least one biopolymer,which is a starch modified by an etherification reaction.

In a third embodiment, the present invention further relates to the useof a biopolymer starch modified by a chemical reaction of etherificationthat enables the link between polymeric chains and some that underwent areduction in the polymeric chain by hydrolysis reaction for thetreatment of acid or alkaline cellulose pulps.

Further, the present invention relates to a process for the preparationof paper, such as printing, writing, decorative, special or tissue-typepapers, through the use of the cellulose pulps modified by the aboveprocess.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an alkaline pulp in the relationbetween tensile index and bulk considering refining effect in a PFImill.

FIG. 2 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an alkaline pulp in the relationbetween the tensile index and the Schopper Riegler value (° SR)considering refining effect in a PFI mill.

FIG. 3 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an alkaline pulp in the relationbetween the tensile index and the Gurley value, considering refiningeffect in a PFI mill.

FIG. 4 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an acid pulp in the relationbetween the tensile index and bulk considering refining effect in a PFImill.

FIG. 5 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an acid pulp in the relationbetween the tensile index and the Schopper Riegler value consideringrefining effect in a PFI mill.

FIG. 6 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an acid pulp in the relationbetween the tensile index and the Gurley value considering refiningeffect in a PFI mill.

FIGS. 7 and 8 show a graph with data about the effect of adding abiopolymer according to the present invention to alkaline and acidpulps, respectively, in the relation between the tensile index andenergy consumption considering refine effect in a pilot plant.

FIG. 9 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an alkaline pulp in the relationbetween the tensile index and bulk considering refine effect in a pilotplant.

FIG. 10 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an alkaline pulp in the relationbetween the tensile index and the Schopper Riegler value consideringrefine effect in a pilot plant.

FIG. 11 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an alkaline pulp in the relationbetween the tensile index and the Gurley value considering refine effectin a pilot plant.

FIG. 12 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an acid pulp in the relationbetween the tensile index and bulk considering refine effect in a pilotplant.

FIG. 13 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an acid pulp in the relationbetween the tensile index and the Schopper Riegler Value consideringrefine effect in a pilot plant.

FIG. 14 shows a graph with data about the effect of adding a biopolymeraccording to the present invention to an acid pulp in the relationbetween the tensile index and the Gurley value considering refine effectin a pilot plant.

FIG. 15 shows a comparison of mechanic resistance between thetissue-type paper produced with cellulose pulp treated by the biopolymerand the tissue-type paper produced with normal cellulose pulp.

FIG. 16 shows a comparative graphic of the soft and mechanic resistanceproperties of the tissue-type paper produced with cellulose pulp treatedby the biopolymer and the tissue-type paper produced with normalcellulose pulp.

FIG. 17 shows the improvement of mechanic resistance and the lost ofthickness of the tissue-type paper produced with cellulose pulp treatedby the biopolymer when comparing to the tissue-type paper produced withnormal cellulose pulp.

FIG. 18 shows the paper average dry content measured after the pressduring the production of the tissue-type paper.

FIG. 19 shows a comparison of mechanic resistance between the woodfreeuncoated paper produced with cellulose pulp treated by the biopolymerand the woodfree uncoated paper produced with normal cellulose pulp(standard).

FIG. 20 shows a comparison of elongation between the woodfree uncoatedpaper produced with cellulose pulp treated by the biopolymer and thewoodfree uncoated paper produced with normal cellulose pulp (standard).

FIG. 21 shows a comparison of solid content between the woodfreeuncoated paper produced with cellulose pulp treated by the biopolymerand the woodfree uncoated paper produced with normal cellulose pulp(standard).

DETAILED DESCRIPTION OF THE INVENTION

The biopolymer developed for the present invention is a polymer ofnatural origin which is submitted to a chemical reaction ofetherification. More specifically, it is a modified starch in such a waythat the hydrogen atom of molecule reactive group is substituted withanother radical: 2,3-epoxypropyl-N-alkyl-N,N dimethylammonium chloride.The biopolymer can be produced from corn starch, manioc starch or anyother plant source of starch.

Preferably, the etherification reaction for modifying the natural starchis carried out in an alkaline medium, in aqueous suspension with a solidcontent of 20% to 65% and under a controlled temperature conditionsbetween 20° to 50° C. during a period of about 8 to 16 hours. In thisreaction medium and using an alkaline catalyst to promote oxydryl groupsactivation, the process renders the starch molecule susceptible to thesubstitution reaction with an epoxide reactive agent(2,3-epoxypropyl-N-alkyl-N,Ndimethylammonium chloride) from(3-chloro-2-hydroxypropyl-trimethylammonium)amide with thestoichiometric addition of an alkali.

The abovementioned chemical modification was verified in biopolymerswith different charges, comprising positive, negative, neutral or mixedcharges wherein a same biopolymer chain has at least two types ofdifferent charges and can be characterized by the Degree of Substitution(DS). This value is determined by the average number, expressed in molarbasis, of hydroxyl groups substituents of each D-glucopyranosyl unitthat is part of the biopolymer. Several biopolymers were assessed withthe DS of the set varying within a range of 0.020 to 0.065.

This modification process confers special characteristics to thebiopolymers which favor their interaction with the fibers and othercellulose pulp components, such as vessels and fines elements. As aresulting benefit from this higher interaction there is an increase inbonds amount between the biopolymers and the several fractions ofcellulose pulps. As a consequence of this procedure, it is possible toobtain an increase in cellulose physical resistance and drainingproprieties.

Biopolymers act on cellulose with the formation of hydrogen bonds bymultiplying the bonds among the fibers and helping to retain fines,which improves the mechanical strength and drainage of the paperproduced in the future. Hydrogen bonds are ionic and considered to beweak; yet, they represent a significant contribution to cellulose andpaper properties. Among them, the biopolymer molecules can form bondswith the creation of crystalline regions having high binding capacitybetween fibers and fines, uniformly forming high resistance clustersdistributed in cellulose and in paper. The intensity of this phenomenonmay vary with specific biopolymers constitution, size distribution andmolecule dispersion, in addition to chemical modifications promoted byother reactions.

Other interactions can be present in the contacts between thebiopolymers of the present invention and cellulose and paper componentssuch as electrostatic attraction and Van der Waals forces. Thisdiversity of biopolymer interactions ensures its permanent effects onpaper final characteristics even after going through cellulose and papermanufacturing process.

The modified biopolymers used in the present invention are selectedaccording to each type of cellulose pulp to be treated and, therefore,according to each type of specific production process, depending onreaction conditions and on the degrees of substitution required for thedesired results.

The inventors have noticed that the addition of these biopolymersspecifically developed for the process of the present invention candifferentiate pulps properties, particularly cellulose pulps ofeucalyptus, with a substantial increase in tensile strength, tearresistance, drainability, and air permeability, among other importantand desired properties. This enables differentiated and innovativeapplications, and the possibility of using more short fibers instead ofthe long fibers, and can result in improvements in plant productivity orenergy savings because it facilitates pulp dewatering in the dryingstage.

As the properties of cellulose treated according to the process of thepresent invention are in-between the short- and long-fiber celluloses,with some important relations among those properties being better thanthose of the original eucalyptus fiber cellulose, the differentiatedcellulose thus obtained can also be considered a new long-fibersubstitution product. Due to the differences obtained for the biopolymerused in the present invention, they can be employed in pulps applied inthe manufacture of different types of papers, such as printing, writing,decorative, special or tissue-type papers, for instance.

It must be, therefore, highlighted that the process of the presentinvention does not refer to the use of a biopolymer in a later stageduring the papermaking process. Rather, it refers to the use of saidbiopolymer during the process of production to obtain modified cellulosewith improved mechanical and drying properties as consequence of thismodification on the cellulose process. The cellulose thus produced isthen dried, repulped, and afterwards goes through the complete processof papermaking. The process of the present invention aims to have thepolymer intimately bonded to the cellulose fibers in order to increasethe number and strength of fiber to fiber bondings. The final objectiveis to increase the mechanical strength of the cellulose. Therefore, theinvention rely on the verification that the mechanism involved in theprocess as claimed in the present application is to form bonds betweenfibers and biopolymer that will remain through the drying andpapermaking process.

Therefore, the modified biopolymers are added to the cellulose pulpbefore said pulp is sent to the paper making process, passing through adrying and packing process of the obtained cellulose. These biopolymersadsorbed in the cellulose fibers can go through a disintegration andrefining process, when cellulose later enters the paper manufacturingprocess. They still retain the special characteristics obtained in themodification of the process of cellulose manufacturing enabling savingssome additives that are typical of certain kinds of papers, which couldbe reduced or eliminated.

In other words, the improved properties (e.g. tensile resistance, tearresistance, drainage resistance and air permeability) of the pulpobtained by the treatment process with the biopolymer are importantsince they facilitate the paper making process.

These improved properties will be promptly transferred to the paperobtained, especially the tissue-type paper and printing paper.Therefore, the mechanical deficiency caused by the increased content ofshort fibers in the paper making process is overcome and importantproperties, such as absorption and softness, are obtained in view of thehigh amount of short fiber.

According to pulp manufacturing process and to the present invention,the addition of the biopolymer can be made in several ways and in atdifferent times in view of the process variables which, in turn, vary inview of pulp desired characteristics. Some of these conditions can beobtained in delignification stage with oxygen, between the bleachingstages or even right after the pulp is bleached.

The process according to the present invention can also be applied tohigh yield pulps, which are pulps that do not go through a more drasticcooking and bleaching process, such as the chemical pulps, and keeptheir yield above 65%, provided they meet the biopolymer applicationconditions. Among the most well-known high yield pulps, mechanical,thermomechanical and chemothermomechanical pulps can be mentioned.

After going through the bleaching process, an additional treatment canbe applied to the cellulose pulp under the required conditions for thebiopolymer to modify said pulp. The biopolymer added in this stage, thatis, after bleaching, should be activated by a cooking process, underconditions to be determined according to the specific characteristics ofthe biopolymer used. In the case of biopolymers that accept alkalineconditions, for example, they can be added in suitable temperature, pHand residence time conditions, in several points of the process, suchas: oxygen delignification and alkaline stages of bleaching. In bothcases, the biopolymers are fixed to the pulp before it is sent to thepaper production process, going through the obtained cellulose drying,baling and rebeating processes without losing the characteristics added.

According to a preferred embodiment of the invention, the process fortreating the cellulose pulp comprises a process of bleaching alkalinepulp having the sequence ADo(Eop)PP wherein the acronyms of thebleaching stages mean: A, the acid stage; Do, the short stage ofchlorine dioxide; Eop, the alkaline extraction stage with small oxygenand hydrogen peroxide doses and P, the hydrogen peroxide dosage stagesand wherein the biopolymer is added between one of the alkaline steps ofbleaching or in an alkaline step before bleaching.

Still in a preferred embodiment, the biopolymer is added to thecellulose pulp during the treatment process in an amount of 5.0 kg/adtto 20.0 kg/adt based on pulp total amount, in a temperature range offrom 45° C. to 95° C., preferably from 70 to 90° C., and with a contacttime between the biopolymer and the pulp in the range of 10 min to 360minutes, preferably from 30 to 90 minutes. Preferably, the pH during theaddition of the biopolymer is from 8 to 11 for alkaline pulps and from 3to 6 for acid pulps.

Behavior assessments of regular variations in the cellulosemanufacturing process relating to the properties of the cellulosemodified with biopolymers according to the present invention should bemade for each production process. In addition, an assessment of theinterference of this new modified cellulose product in the propertiesand in the manufacturing process of different types of papers should becarefully developed for the application of cellulose modified withbiopolymers, and such parameters may be promptly determined by skilledartisans and do not represent an essential and determinantcharacteristic of the present invention.

EXAMPLES

The following examples will better illustrate the present invention, andthe particular conditions and parameters described represent preferred,and non-limiting, embodiments of the present invention.

Process for the Treatment of Cellulose Pulps

Example 1

For a alkaline pulp treating process, it was used a biopolymer hereinidentified as “AlcBio1”, referring to a hybrid corn polysaccharidechemically modified by etherification in the following conditions: pH of8.5 in aqueous suspension with 30% of solids concentration and acontrolled temperature of 30° C., during a period of 8 hours. Itsphysical aspect corresponds to a fine white powder having acharacteristic starch odor, insoluble in water and organic solvents.With regard to its chemical characterization, said biopolymer AlcBio1has a degree of substitution of 0.025 to 0.045, hydrogenionic potential(pH) of 5.5 to 6.5 and maximum humidity of 14%.

Example 2

For alkaline pulp treating process, it was used a biopolymer hereinidentified as “AlcBio2”, referring to a corn polysaccharide chemicallymodified by etherification in the following conditions: pH of 8.5 inaqueous suspension with 40% solids concentration and a controlledtemperature of 40° C., during a period of 6 hours. Its physical aspectcorresponds to a fine, white powder, insoluble in water and organicsolvents. With regard to its chemical characterization, said biopolymerAlcBio2 has an amphoteric charge (positive and negative) with a degreeof substitution of 0.025 to 0.042, hydrogenionic potential (pH) of 5.5to 6.5 and maximum humidity of 14%.

Example 3

For alkaline pulp treating process, it was used a biopolymer hereinidentified as “AlcBio3”, referring to a corn polysaccharide chemicallymodified by etherification in the following conditions: pH of 9.0, inaqueous suspension with 35% of solids concentration and a controlledtemperature of 30° C., during a period of 8 hours. Its physical aspectcorresponds to a fine white powder, insoluble in water and organicsolvents. With regard to its chemical characterization, said biopolymerAlcBio3 has anionic charge, hydrogenionic potential (pH) of 5.5 to 6.5and maximum humidity of 14%.

Example 4

For acid pulp treating process, because of process conditionsrequirements, the biopolymer herein identified as “AcBio2” was used,which is an aqueous solution formed by a starch polysaccharidechemically modified as previously described having the degree ofsubstitution in the range of from 0.022 to 0.040, pH of 5.0 to 6.0, andcontaining preservative based on benzisothiazolinone. This preservativewas needed to avoid degradation of the product, which is quitesusceptible to attacks of microorganisms. Biopolymer AcBio2 has thefollowing physical features: cream color viscous solution,characteristic odor of starch, maximum bulk density of 1.13 g/cm³, solidcontents of 24.0% to 27.5%, maximum viscosity of 2000 cP, andhydrogenionic potential (pH) of 5.5 to 7.5.

Comparative Test Results

With these examples of biopolymers AlcBio1 (alkaline process) and AcBio2(acid process), laboratory tests, intermediate and industrial scaletests were carried out. The results obtained in these cases showimportant developments on modified cellulose properties. In laboratoryscale, the equipment used was a cellulose bleaching reactor with a 300 gdry fibers capacity, and total automatic control of the processconditions. In the preindustrial scale test of the process, the reactorused, which had a 100 kg dry pulp capacity, also had automatic controlof the process variables. However, in this case, the addition andshearing conditions were closer to the industrial conditions due topumping operations and loss of load during cellulose transportation.

Optimized procedures with alkaline pH pulp were developed to use thebiopolymer without interfering in the cellulose manufacturing process.To this end, the biopolymer was added between the two stages of hydrogenperoxide, within the sequence used for cellulose bleaching. In thisstage, the bleaching conditions, which were compatible for theapplication of the biopolymer, were: pH—11.0, temperature—90° C.,consistency—10% and retention time—80 minutes. For these conditions,biopolymer AlcBio1 was chosen. This biopolymer was dosed in severalquantities relating to the percentage of dry fiber with a view tooptimizing its dosage.

Biopolymer application to alkaline cellulose was done in-between thebleaching stages, because these technical conditions were the mostadvantageous for activating their desired contributions. However, otheralkaline stages can also receive said biopolymers dosage with equallyadvantageous results with regard to the base pulp.

Other studies in larger scale were also carried out, including assessingthe refining capacity of the resulting pulp so as to confirm theadvantages obtained with the present procedure. As expected, the resultswere proportionally increased in relation to the dosed quantities.However, as the dosage effect is not linear, a cost/benefit analysisshows that the dosage can be optimized with the use of this process inindustrial scale, but it is currently around 0.5 to 1.5%. Part of theresults shown later in this document relate to 1.5% dosages of thebiopolymer AlcBio1 in these conditions.

Cellulose modification development with biopolymers was complemented ina second step with the modification of the acid pulp, as indicated inexample 2. The purpose of this study was to improve the development of abiopolymer suitable for the many acid pH conditions noticed in celluloseproducing process. This dosage required other biopolymers types, sincethe process conditions are different and incompatible with thebiopolymers used in the previous process, which is alkaline. Thebiopolymers that will be added to cellulose in acid pH should beactivated out of the cellulose production process, before theiraddition. In this case, the biopolymer AcBio2 was obtained and issuitable for cellulose producing process with application in the pulp inthe end of the bleaching process. Said biopolymer AcBio2 was applied inthe following conditions: pH—5.5; temperature—70° C.; consistency—10%and retention time—30 minutes. The biopolymer dosage is similar to thedescribed in alkaline pulps, and the results are also as satisfactory asthose achieved with these pulps. This condition can be facilitated ifthe last stage of bleaching is acid. In this case, an effective mixturewith the pulp significantly contributes to the effect of the biopolymerbefore a probable dilution of cellulose in later operations process.

The studies carried out with the biopolymers of the present inventionshow that, although the results are not linear, the properties gain isdirectly proportional to the additive amount added, which advantageouslycan be from 5.0 kg/adt to 20.0 kg/adt. From the samples selected for thepilot test, one was applied in the alkaline condition and the other inthe acid condition according to the possible success rates for workingwith these biopolymers within the cellulose manufacturing process.

The initial experimental work of the present invention includedlaboratory tests for sole application in pulps produced in alkaline pHbecause the process conditions for such cellulose seemed to be the mostsuitable for the required development. Actually, after multiple testsand modifications to the biopolymers, the results were positive in theseconditions. After these first results, biopolymers development for usein pulps with acid pH was less expensive and the results obtained wereequally positive.

After defining process conditions, the product dosages were alsooptimized. Although the amount added is also linked with developmentscale, as seen in the test carried out in the pilot plant. The testsmade in the pilot plant, in the conditions used in the laboratory, butin reactor with a 100 kg dry pulp capacity, showed the same improvementtendency of interest properties. The biopolymer in this case should bediluted in potable water or in wash water of the bleaching stages withmaximum distribution and mixing with the pulp that receives it.

Both cases tested enhanced the mechanical strength and drainageproperties in spite of the different characteristics of the biopolymersapplied. Despite the costs involved with the biopolymers added in thisinvention, compensation was detected in pulp refining for paperproduction when this operation is obviously required. Refining showsthat for this differentiated pulp with a biopolymer the required energyto arrive the same drainability degree and mechanical strength is lowerthan that needed for the pulp with the same fiber without the presenceof biopolymer, in all process conditions tested. Obviously, thisadvantage should vary according to the refining technology used andpaper type where this cellulose is applied.

First of all, some important results are presented for alkaline pulpsobtained in laboratory scale.

The results shown in FIG. 1 demonstrate the relation between the tensileindex, as the first property to be developed as reference, that is, thepurpose was to increase the mechanical strength of the pulp alsoproviding a positive relation with other important properties.Biopolymer addition according to the invention shows that there is anincrease in the tensile strength and bulk within the studied grindingcurve; for the same bulk the increase in the tensile index is verysignificant, and vice-versa.

The amount of biopolymer AlcBio1 added in the experiment was 1.5%biopolymer over the dry mass of the substrate to be treated.

The relation between the tensile index and the Schopper Riegler value (°SR) (a measurement of the rate at which a diluted pulp suspension may bede-watered) shown in FIG. 2 demonstrates that, with the use ofbiopolymer AlcBio1, a pulp with higher mechanical strength and lowerenergy cost was obtained for drying the same amount of pulp or anincreasing the production of the plant with the same energy consumption.

Other parameter measured was the relation between the tensile index andthe Gurley value (measure of how fast a defined volume of air can passthrough a defined area of membrane at standard pressure), whichcharacterizes the air permeability of the cellulose pulp sheet. Theresults are shown in FIG. 3. This property is especially interesting dueto its development during the process of grinding in the PFI laboratorymill. The increase in air permeability can also imply an improvement inthe drying process, especially in the paper machine where cellulose hasgone through the refining process.

In the case of acid cellulose, similar analyzes were carried out usingthe knowledge acquired in the previous case. For this study, biopolymerAcBio 2 was used with the specification of the degree of substitution0.022 to 0.040 and pH of 5.0 to 6.0. The biopolymer amount added in theexperiment was 1.5% biopolymer over the dry mass of the substrate to betreated.

As can be observed by the results, the gains in all properties weresimilar, considering the large difference between the biopolymers andthe dosage points among the pulps being studied. The relation betweenthe tensile index and bulk shows an increase in the tensile index andbulk in the entire grinding range studied in the laboratory experiments.In the case of acid pulps, it is evident that the tensile gain for thepulps with biopolymers is higher than that with the original pulps(white), for the same amount of energy applied (FIG. 4).

The relations between the tensile index and the Schopper Riegler value(° SR) for the acid pulps with and without biopolymer shown in FIG. 5are higher than the results for the alkaline pulps. However, thisbenefit is very important in alkaline pulps because of their highergreater draining difficulty.

FIG. 6 shows a decrease in air resistance with the application ofbiopolymer for the acid pulp.

These were the properties with the highest interest among thoseinvestigated, which show the invention efficacy in developing importantproperties that are constantly requested by customers of short-fibercellulose. Other properties such as tear and opacity also showadvantages with the application of biopolymers according to the presentinvention.

To confirm the values obtained on laboratory scale, a pilot test wasconducted in a plant with a 100 kg pulp capacity, considering air-driedfibers. The pilot plant, in which the cellulose treated with biopolymersproduced according to the process of the invention, consists of adilution tank, wherein the pulp was prepared under the requiredconditions and a mixer that receives the required reagents. In thiscase, the reagents and the process conditions were similar to those usedin the laboratory. The reagent is only the biopolymer added to the pulpat 10% consistency and the process conditions were exactly the same witha residence time of 60 minutes, temperature of 60° C. and reactorrotation of about 28 rpm.

After going through the mixer, the pulp enters the reactor where thereaction conditions and the retention time were preserved. After thereactor, the pulp went through a discharge tank and a dewatering tablethat enabled the pulp to reach up to 35% dryness. Drying was concludedin a drying room under controlled temperature and humidity conditions sothat the pulp properties were not affected by hornification other thanby traditional cellulose drying.

The obtained pulps were refined in pilot plant refiners with 12-inchdiameter disks. The disks employed enabled the use of a very lowintensity refining technology, which is proper for eucalyptus cellulose.The results of such refining show substantial energy savings for pulpswith biopolymers of the present invention compared with commoneucalyptus pulps, using as basis the same mechanical strength expressedin the cellulose tensile index, as can be seen in the drawings.

The drawings refer to alkaline and acid pulps which are refined in thepapermaking process, which in both cases represent energy gains for thepaper manufacturer with biopolymer use. The drawings also clearlyindicate that energy amounts applied during refining in pilot plants,which should be related with properties magnitude shown in the sequence.

FIG. 7 compares a reference pulp with another pulp with the applicationof 1.0% biopolymer AlcBio1 and the same energy was used for both pulps.The comparison of theses pulps shows that energy can be saved to obtainthe same mechanical strength through refining.

Under similar comparison conditions, FIG. 8 shows the refining resultsin a pilot plant for acid pulps. The properties analyzed in the sequencerefer to the pulps obtained and refined in a pilot plant, thereforesubmitted to different treatments and stresses than the pulps obtainedand treated in the laboratory scale. The results obtained alsocorroborate the results on laboratory scale showing the same gaintendency of the same properties analyzed. In this case, there is also animprovement in the mechanical strength and drainage properties, whichare two characteristics that potentiate the application of this modifiedcellulose.

FIG. 9 shows a small bulk gain with the addition of 1.0% biopolymer inalkaline pulp, the results in the industrial application should besimilar to these results or even better due to better processconditions. The increasing bulk effect is always advantageous forcellulose.

The drainability effect for the alkaline pulp shown in FIG. 10 alsofollowed a positive tendency reiterating the results on laboratoryscale.

FIG. 11 shows the positive effect achieved with biopolymer applicationof the present invention in air permeability increase of cellulose,which grows as the refining effects intensify.

In the case of acid pulp, the tendency is also to have a bulk increasewith biopolymer presence throughout the refining curve in the pilotplant. This result is coherent with alkaline pulp effects, and theresults on laboratory scale show that these gains can be better (FIG.12).

FIG. 13 shows the gain in Schopper Riegler value during the developmentof refining in a pilot plant. This represents a property gain with lowerenergy consumption or even a possible increase in the productivity ofthe cellulose drying machine and the paper machine, with the samemechanical strength properties.

FIG. 14 shows the refining curves for the Gurley value, following thesame tendency of the alkaline cellulose and of the laboratory scaletests, shows a decreasing in air permeability resistance, which ismeasured with the Gurley equipment, as a biopolymer contribution. Thisadvantage increases with refining development.

All the presented results are evidences of cellulose modifications and,more than that, they show that the interrelationships among importantproperties are positively changed bringing greater benefits to celluloseapplication. These modifications result in the possibility of havingintermediate applications in-between the properties of short- andlong-fiber celluloses having a great substitution potential withpercentage advantages of the long fibers in the paper recipes,especially in tissue paper and in printing and writing papers.

Process for Making Paper using the Treated Cellulose Pulp

In order to demonstrate the superiority of the paper produced fromcellulose pulp modified by the biopolymer according to treating processdisclosed above, samples of tissue paper type paper, more specificallytoilet paper, and printing and writing were prepared.

Nevertheless, before describing the details of the examples, it isnecessary provide some important definitions in order to support thedescription of the present invention:

“Short-fiber pulp” means a pulp originated from woods such asEucalyptus, but that can also include other species such as Acacia,Birch, Maple, among others, since the short-fibers characteristics thatcan affect the relevant paper properties in the present invention aresimilar to these woods.

“Bleached chemical pulp” means pulp obtained by the chemical process ofcooking and bleaching. This pulp is specially used in the manufacture oftissue-type paper.

“Eucalyptus natural fiber” means natural fibers that were obtained by achemical process of pulping and bleaching without additives unrelated tothe process used.

“Modified Eucalyptus fiber” means Eucalyptus fiber modified by themodified biopolymer.

“Fibrous structure” means a structure formed by a fibrous web due to theintertwining of fibers by the previous preparation of fiber andsubsequent deposition of an amount of fiber, usually on a screen or afelt, in order to form the structure. Typically in the manufacture ofpaper, whatever its type, this structure is formed on a screen, driedand rolled into a coil.

In the manufacture process of tissue-type paper, the structured leavesare produced with pressing regions with smaller areas of high densityand other regions with larger areas of high bulk, softness and liquidsabsorption capacity. The traditional structures are flat wherein theleaf is only formed on a flat screen.

The structure of writing and printing paper was also formed in a flatstructure in a traditional Fourdrinier machine.

Description of the Production of Tissue-Type Paper

The tissue-type papers produced with the modified cellulose were papertowel (with a paper density of 21 g/m²) and toilet paper (with a paperdensity of 16 g/m²) on machines with standard configuration. Theformulation of these papers is typical for most producers of highquality papers, with 75% of short-fiber and 25% of long-fiber for thetoilet paper, and with 70% of short-fiber and 30% of long-fiber for thepaper towel. The long-fiber is normally refined to ensure the mechanicalstrength and to increase the short-fiber content, but the same degree ofrefinement was used for all paper manufactured. The additives selectedfor this paper production are also the typical used in producing thesetypes of tissue papers, such as wet strength agent and dry strengthagent.

The machine used for this paper manufacturing is in a pilot scale, withwidth of 1,000 mm and speed of 1,000 m/min, with Crescent Former andconventional press with suction against the Yankee cylinder, and a dailyproduction of 3 tons of paper. The paper is dried on Yankee cylinder androlled into coils. This machine allows samples to be crepes, with anangle variation of the creping, or rolled flat.

In the mass preparation, the samples of short-fiber and long-fiber weredisintegrated in a pulper where they also receive the necessary chemicaladditives. For the toilet paper preparation, starch was added as drystrength agent, and for the paper towel preparation, the Kymene® productfrom Ahsland, cationic resin (to improve wet strength) andcarboxymethylcellulose were added. The long-fiber was refined and mixedwith short-fiber to enter the machine.

Table 1 shows the principal variations during the toilet papermanufacturing in said pilot machine.

TABLE 1 principal variations during the toilet paper manufacturing insaid pilot machine Vacuum SPR Yankee Temperature Paper Pressure UhleboxStraight load Speed Pressure Hood Surface Scraper Paper Jumb roll Type(bar) (bar) (kN/m) (m/min) (bar) ° C. ° C. ° C. ° C. Toilet 1 0.23 0.5690 1000 6.5 90 83 47 0.23 0.58 90 1000 6.5 434 96 91 50 0.24 0.58 901000 6.5 438 — — 52 0.24 0.58 90 1000 6.5 440 89 83 49 0.24 0.58 90 10006.5 440 89 83 49 0.24 0.58 90 1000 6.5 469 — — — Average 444 Toilet 20.24 0.58 90 1000 6.5 — — — 0.24 0.58 90 1000 6.5 477 — — — 0.24 0.58 901000 6.5 477 — — — 0.24 0.58 90 1000 6.5 93 102 57 0.25 0.58 90 1000 6.5483 94 100 55 0.25 0.58 90 1000 6.5 482 96 87 54 0.25 0.58 90 1000 6.5472 101 89 56 Average 478 Toilet 3 0.24 0.58 90 1000 6.5 97 88 54 0.250.58 90 1000 6.5 462 93 84 54 0.25 0.58 90 1000 6.5 459 91 82 54 0.250.58 90 1000 6.5 458 86 81 52 0.25 0.58 90 1000 6.5 456 88 80 50 Average459

The samples tested were papers produced with cellulose modified by abiopolymer (modified pulp) and with regular eucalyptus cellulose pulp(reference pulp), which will form the basis for a comparative analysis.The difference between the paper towel and toilet paper produced ismainly in the paper density and the addition of different wet strengthagent.

The data here represented refers to the tests of toilet paper, which aremost sensitive to changes in the pulp due to the minor addition ofchemical agents that interfere in the process and the lower paperdensity of the formed sheet.

During the test, the values of paper density, bulk and mechanic strengthwere measured in 19 rolls removed from the machine in comparable processconditions and with a constant paper density so that the properties ofthe paper made from modified pulp and the paper made from reference pulpcould be compared.

For the toilet paper made from reference pulp, the paper grammage of 17g/m² and tensile of 400 gf/50 mm in the machine direction (MD) and of200 gf/50 mm in the cross direction (CD) were specified. For the towelpaper, the paper grammage of 20 g/m² and tensile of 1200 gf/50 mm in themachine direction (MD) and of 800 gf/50 mm in the cross direction (CD)were specified.

The properties obtained with the web of structured fiber of thereference pulp and of structured fiber of modified pulp showedsignificant differences. The property with more improvement was themechanical strength of the paper, which was measured as tensile thatdirectly increases when the addition of biopolymers also rises.

Another test carried out during the production of toilet paper was theaddition of starch in the machine approach flow, which is usually partof this process of production, where starch is used as dry strength aid.In this case, an impressive increase of tensile occurred with thecellulose modified with 1.0% of biopolymer plus the addition of 6.0kg/ton, when comparing to the reference pulp. This property hasincreased (with cellulose modified) by about 150% in the machinedirection, where the fiber is more lined, and has also increased by 169%in the cross direction, as shown in FIG. 15.

These tensile increases are confirmed when geometric average isperformed between the tensile measured in the longitudinal andtransverse directions, i.e. in this case the fibers direction areminimized. In this case, the tensile containing modified cellulose with1.0% of biopolymer plus 6.0 kg/ton of starch.

Another important factor was the increased adherence of the sheet in theYankee cylinder with the modified cellulose, i.e., there was a visibleimprovement in the crepe of the tissue paper with the increasing of thelinear count of the crepe, hence the softness of paper raised and theapplication of adhesive on the Yankee cylinder decreased about 20%.

From the analysis of FIG. 16, that shows a comparison of these twoimportant properties, it can be concluded that a great increase of thetensile allows adjustments in the fibers formulation of the process inorder to improve the quality of the final paper. Moreover, thesignificant increase of the mechanical strength allows a cost saving dueto the replacement of long-fibers by short-fibers, or a saving of theenergy used to refine the long-fiber, or a decreasing in paper densityper layer of the produced paper.

Therefore, a larger amount of short-fibers results in an increasingsoftness of the paper, as well as a better adherence of the paper sheetto the Yankee cylinder or a decreasing in the degree of refining oflong-fiber promotes a better quality of the paper, see FIG. 17.

Another improvement in the paper production with the modified cellulosewas the increasing of paper dryness along the machine, in other words,the machine productivity increases and/or the specific energyconsumption decreases, depending on the evolution of the profile contentdry, see FIG. 18.

Description of the Production of Printing and Writing Paper

The production of printing and writing paper was performed on aFourdrinier machine. This offset base paper with a grammage of 57 g/m²is the basis for the production of heat-sensitive paper, produced on P1machine.

The purpose of this test is to compare the performance in paper machineand the properties obtained from standard cellulose pulp (standard pulp)and cellulose modified with 1.0% of biopolymer (modified pulp).

The production of this paper comprises the addition of mineral filler,starch in the mass and in the surface, as dry strength agent, and gluein order for repellence of water. The paper is manufactured from 100% ofshort fiber being refined to a certain Schopper Riegler degree that waskept for the two evaluated fibers.

The standard specifications of the machine were kept as constant aspossible. The paper production machine was normal from the cellulosedisintegration to obtain the final paper roll. A positive behaviornoticed during the paper production with the modified pulp was theincrease of the bulk so that calendering had to be maximized to keep thepaper caliper specification.

As can be observed through results of this test, represented in FIGS. 19to 21, the paper produced with the cellulose pulp modified by thebiopolymer obtained the best results.

FIG. 19 shows an increase of 4% in tensile of the paper with modifiedpulp. This represents a tendency also observed in manufacturing oftissue-type paper.

FIG. 20 shows higher values of elongation for the paper produced withmodified pulp. Due to the elastic nature of the connections of thebiopolymer and the high number of bounds formed with the fibers, it isexpected that the elongation capacity of the paper increases.

The reducing of solid content before the press is very important for thepaper making process, because it represents an increasing in theproduction and an energy savings. The water removed from the presses andin the drying step is the most difficult to extract and therefore moreexpensive. The gain value of solid content is shown in FIG. 21 that hasa positive result in financial production of paper machine.

The invention claimed is:
 1. A process for treating cellulose pulpscomprising a step of adding at least one biopolymer during the bleachingprocess of the pulp, said biopolymer being added in an amount of 5.0kg/adt to 20.0 kg/adt based on the total amount of pulp, with pH from 3to 11, characterized in that said biopolymer is starch modified by thechemical reaction of etherification.
 2. The process, according to claim1, wherein said biopolymer is chemically modified starch from naturalsources selected from corn or manioc.
 3. The process, according to claim1, characterized in that the biopolymer is added, together with regularbleaching chemicals, in any of the alkaline stages of an and/or afterthe bleaching sequence but prior to pulp drying.
 4. The process,according to claim 1, characterized in that the biopolymer is addedapproximately at 45° C. to 95° C. with a contact time between thebiopolymer and the pulp in the range of from 10 to 360 minutes.
 5. Theprocess, according to claim 1, wherein said biopolymer includes areactive group of 2,3-epoxypropyl-N-alkyl-N,N dimethylammonium chloride.